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Self-Assembly and Host-Guest Interactions of Pd3L2 Metallo-cryptophanes with Photoisomerizable Ligands
Edward Britton1, Richard J Ansell1, Mark J Howard1
1School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
Inorganic Chemistry
|August 9, 2021
Summary
New photoswitchable ligands were used to create palladium-based coordination cages. These cages can bind anions and organic molecules, but are less stable than iridium-based cages, showing the importance of metal-ligand bond strength.
Area of Science:
- Supramolecular Chemistry
- Coordination Chemistry
- Materials Science
Background:
- Cyclotriveratrylene-based tripodal ligands offer unique structural scaffolds for host-guest chemistry.
- Photoswitchable ligands introduce dynamic control over supramolecular structures.
- Metallacryptophanes are cage-like coordination complexes with potential applications in molecular recognition.
Purpose of the Study:
- To synthesize and characterize new photoswitchable pyridyl-azo-phenyl-decorated tripodal host ligands (Laz).
- To construct and investigate the properties of trigonal bipyramidal palladium(II) metallo-cryptophanes using these ligands.
- To evaluate the host-guest capabilities and stability of the palladium cages.
Main Methods:
- Synthesis and structural determination (X-ray crystallography) of new photoswitchable ligands.
- Formation and characterization of palladium(II) coordination cages.
- Investigation of photoswitching behavior and stability under varying conditions.
- Binding studies with anionic and neutral guest molecules in solution.
Main Results:
- Successful synthesis of photoswitchable pyridyl-azo-phenyl-decorated tripodal host ligands (Laz).
- Crystal structure revealed a 7-fold Borromean-weave entanglement of π-π stacked layers.
- Trigonal bipyramidal {[Pd(en)]3(Laz)2}6+ metallo-cryptophanes were formed.
- These palladium cages exhibit host-guest behavior, binding octyl sulfate anions and an N-naphthalimide derivative.
- The palladium cages showed lower robustness to photoswitching and dissociation compared to related iridium cages.
Conclusions:
- The synthesized photoswitchable ligands enable the formation of dynamic palladium-based metallo-cryptophanes.
- The lability of Pd-N bonds influences the stability and photoswitching robustness of the coordination cages.
- These cages demonstrate potential for molecular recognition and host-guest chemistry, with stability being a key consideration for applications.
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